lib-src/update-game-score.c

   1 /* update-game-score.c --- Update a score file
   2
   3 Copyright (C) 2002-2013 Free Software Foundation, Inc.
   4
   5 Author: Colin Walters <walters@debian.org>
   6
   7 This file is part of GNU Emacs.
   8
   9 GNU Emacs is free software: you can redistribute it and/or modify
  10 it under the terms of the GNU General Public License as published by
  11 the Free Software Foundation, either version 3 of the License, or
  12 (at your option) any later version.
  13
  14 GNU Emacs is distributed in the hope that it will be useful,
  15 but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 GNU General Public License for more details.
  18
  19 You should have received a copy of the GNU General Public License
  20 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  21
  22
  23 /* This program allows a game to securely and atomically update a
  24    score file.  It should be installed setuid, owned by an appropriate
  25    user like `games'.
  26
  27    Alternatively, it can be compiled without HAVE_SHARED_GAME_DIR
  28    defined, and in that case it will store scores in the user's home
  29    directory (it should NOT be setuid).
  30
  31    Created 2002/03/22.
  32 */
  33
  34 #include <config.h>
  35
  36 #include <unistd.h>
  37 #include <errno.h>
  38 #include <limits.h>
  39 #include <string.h>
  40 #include <stdlib.h>
  41 #include <stdio.h>
  42 #include <time.h>
  43 #include <pwd.h>
  44 #include <ctype.h>
  45 #include <fcntl.h>
  46 #include <sys/stat.h>
  47 #include <getopt.h>
  48
  49 #define MAX_ATTEMPTS 5
  50 #define MAX_SCORES 200
  51 #define MAX_DATA_LEN 1024
  52
  53 #ifndef HAVE_DIFFTIME
  54 /* OK on POSIX (time_t is arithmetic type) modulo overflow in subtraction.  */
  55 #define difftime(t1, t0) (double)((t1) - (t0))
  56 #endif
  57
  58 static _Noreturn void
  59 usage (int err)
  60 {
  61   fprintf (stdout, "Usage: update-game-score [-m MAX] [-r] [-d DIR] game/scorefile SCORE DATA\n");
  62   fprintf (stdout, "       update-game-score -h\n");
  63   fprintf (stdout, " -h\t\tDisplay this help.\n");
  64   fprintf (stdout, " -m MAX\t\tLimit the maximum number of scores to MAX.\n");
  65   fprintf (stdout, " -r\t\tSort the scores in increasing order.\n");
  66   fprintf (stdout, " -d DIR\t\tStore scores in DIR (only if not setuid).\n");
  67   exit (err);
  68 }
  69
  70 static int lock_file (const char *filename, void **state);
  71 static int unlock_file (const char *filename, void *state);
  72
  73 struct score_entry
  74 {
  75   long score;
  76   char *username;
  77   char *data;
  78 };
  79
  80 static int read_scores (const char *filename, struct score_entry **scores,
  81                         int *count);
  82 static int push_score (struct score_entry **scores, int *count,
  83                        int newscore, char *username, char *newdata);
  84 static void sort_scores (struct score_entry *scores, int count, int reverse);
  85 static int write_scores (const char *filename,
  86                          const struct score_entry *scores, int count);
  87
  88 static _Noreturn void
  89 lose (const char *msg)
  90 {
  91   fprintf (stderr, "%s\n", msg);
  92   exit (EXIT_FAILURE);
  93 }
  94
  95 static _Noreturn void
  96 lose_syserr (const char *msg)
  97 {
  98   fprintf (stderr, "%s: %s\n", msg, strerror (errno));
  99   exit (EXIT_FAILURE);
 100 }
 101
 102 static char *
 103 get_user_id (void)
 104 {
 105   struct passwd *buf = getpwuid (getuid ());
 106   if (!buf)
 107     {
 108       long uid = getuid ();
 109       char *name = malloc (sizeof uid * CHAR_BIT / 3 + 1);
 110       if (name)
 111         sprintf (name, "%ld", uid);
 112       return name;
 113     }
 114   return buf->pw_name;
 115 }
 116
 117 static const char *
 118 get_prefix (int running_suid, const char *user_prefix)
 119 {
 120   if (!running_suid && user_prefix == NULL)
 121     lose ("Not using a shared game directory, and no prefix given.");
 122   if (running_suid)
 123     {
 124 #ifdef HAVE_SHARED_GAME_DIR
 125       return HAVE_SHARED_GAME_DIR;
 126 #else
 127       lose ("This program was compiled without HAVE_SHARED_GAME_DIR,\n and should not be suid.");
 128 #endif
 129     }
 130   return user_prefix;
 131 }
 132
 133 int
 134 main (int argc, char **argv)
 135 {
 136   int c, running_suid;
 137   void *lockstate;
 138   char *user_id, *scorefile;
 139   const char *prefix, *user_prefix = NULL;
 140   struct stat buf;
 141   struct score_entry *scores;
 142   int newscore, scorecount, reverse = 0, max = MAX_SCORES;
 143   char *newdata;
 144
 145   srand (time (0));
 146
 147   while ((c = getopt (argc, argv, "hrm:d:")) != -1)
 148     switch (c)
 149       {
 150       case 'h':
 151         usage (EXIT_SUCCESS);
 152         break;
 153       case 'd':
 154         user_prefix = optarg;
 155         break;
 156       case 'r':
 157         reverse = 1;
 158         break;
 159       case 'm':
 160         max = atoi (optarg);
 161         if (max > MAX_SCORES)
 162           max = MAX_SCORES;
 163         break;
 164       default:
 165         usage (EXIT_FAILURE);
 166       }
 167
 168   if (optind+3 != argc)
 169     usage (EXIT_FAILURE);
 170
 171   running_suid = (getuid () != geteuid ());
 172
 173   prefix = get_prefix (running_suid, user_prefix);
 174
 175   scorefile = malloc (strlen (prefix) + strlen (argv[optind]) + 2);
 176   if (!scorefile)
 177     lose_syserr ("Couldn't allocate score file");
 178
 179   strcpy (scorefile, prefix);
 180   strcat (scorefile, "/");
 181   strcat (scorefile, argv[optind]);
 182   newscore = atoi (argv[optind+1]);
 183   newdata = argv[optind+2];
 184   if (strlen (newdata) > MAX_DATA_LEN)
 185     newdata[MAX_DATA_LEN] = '\0';
 186
 187   user_id = get_user_id ();
 188   if (user_id == NULL)
 189     lose_syserr ("Couldn't determine user id");
 190
 191   if (stat (scorefile, &buf) < 0)
 192     lose_syserr ("Failed to access scores file");
 193
 194   if (lock_file (scorefile, &lockstate) < 0)
 195     lose_syserr ("Failed to lock scores file");
 196
 197   if (read_scores (scorefile, &scores, &scorecount) < 0)
 198     {
 199       unlock_file (scorefile, lockstate);
 200       lose_syserr ("Failed to read scores file");
 201     }
 202   push_score (&scores, &scorecount, newscore, user_id, newdata);
 203   sort_scores (scores, scorecount, reverse);
 204   /* Limit the number of scores.  If we're using reverse sorting, then
 205      also increment the beginning of the array, to skip over the
 206      *smallest* scores.  Otherwise, just decrementing the number of
 207      scores suffices, since the smallest is at the end. */
 208   if (scorecount > MAX_SCORES)
 209     {
 210       if (reverse)
 211         scores += (scorecount - MAX_SCORES);
 212       scorecount = MAX_SCORES;
 213     }
 214   if (write_scores (scorefile, scores, scorecount) < 0)
 215     {
 216       unlock_file (scorefile, lockstate);
 217       lose_syserr ("Failed to write scores file");
 218     }
 219   unlock_file (scorefile, lockstate);
 220   exit (EXIT_SUCCESS);
 221 }
 222
 223 static int
 224 read_score (FILE *f, struct score_entry *score)
 225 {
 226   int c;
 227   if (feof (f))
 228     return 1;
 229   while ((c = getc (f)) != EOF
 230          && isdigit (c))
 231     {
 232       score->score *= 10;
 233       score->score += (c-48);
 234     }
 235   while ((c = getc (f)) != EOF
 236          && isspace (c))
 237     ;
 238   if (c == EOF)
 239     return -1;
 240   ungetc (c, f);
 241 #ifdef HAVE_GETDELIM
 242   {
 243     size_t count = 0;
 244     if (getdelim (&score->username, &count, ' ', f) < 1
 245         || score->username == NULL)
 246       return -1;
 247     /* Trim the space */
 248     score->username[strlen (score->username)-1] = '\0';
 249   }
 250 #else
 251   {
 252     int unameread = 0;
 253     int unamelen = 30;
 254     char *username = malloc (unamelen);
 255     if (!username)
 256       return -1;
 257
 258     while ((c = getc (f)) != EOF
 259            && !isspace (c))
 260       {
 261         if (unameread >= unamelen-1)
 262           if (!(username = realloc (username, unamelen *= 2)))
 263             return -1;
 264         username[unameread] = c;
 265         unameread++;
 266       }
 267     if (c == EOF)
 268       return -1;
 269     username[unameread] = '\0';
 270     score->username = username;
 271   }
 272 #endif
 273 #ifdef HAVE_GETLINE
 274   score->data = NULL;
 275   errno = 0;
 276   {
 277     size_t len;
 278     if (getline (&score->data, &len, f) < 0)
 279       return -1;
 280     score->data[strlen (score->data)-1] = '\0';
 281   }
 282 #else
 283   {
 284     int cur = 0;
 285     int len = 16;
 286     char *buf = malloc (len);
 287     if (!buf)
 288       return -1;
 289     while ((c = getc (f)) != EOF
 290            && c != '\n')
 291       {
 292         if (cur >= len-1)
 293           {
 294             if (!(buf = realloc (buf, len *= 2)))
 295               return -1;
 296           }
 297         buf[cur] = c;
 298         cur++;
 299       }
 300     score->data = buf;
 301     score->data[cur] = '\0';
 302   }
 303 #endif
 304   return 0;
 305 }
 306
 307 static int
 308 read_scores (const char *filename, struct score_entry **scores, int *count)
 309 {
 310   int readval, scorecount, cursize;
 311   struct score_entry *ret;
 312   FILE *f = fopen (filename, "r");
 313   if (!f)
 314     return -1;
 315   scorecount = 0;
 316   cursize = 16;
 317   ret = (struct score_entry *) malloc (sizeof (struct score_entry) * cursize);
 318   if (!ret)
 319     return -1;
 320   while ((readval = read_score (f, &ret[scorecount])) == 0)
 321     {
 322       /* We encountered an error.  */
 323       if (readval < 0)
 324         return -1;
 325       scorecount++;
 326       if (scorecount >= cursize)
 327         {
 328           cursize *= 2;
 329           ret = (struct score_entry *)
 330             realloc (ret, (sizeof (struct score_entry) * cursize));
 331           if (!ret)
 332             return -1;
 333         }
 334     }
 335   *count = scorecount;
 336   *scores = ret;
 337   return 0;
 338 }
 339
 340 static int
 341 score_compare (const void *a, const void *b)
 342 {
 343   const struct score_entry *sa = (const struct score_entry *) a;
 344   const struct score_entry *sb = (const struct score_entry *) b;
 345   return (sb->score > sa->score) - (sb->score < sa->score);
 346 }
 347
 348 static int
 349 score_compare_reverse (const void *a, const void *b)
 350 {
 351   const struct score_entry *sa = (const struct score_entry *) a;
 352   const struct score_entry *sb = (const struct score_entry *) b;
 353   return (sa->score > sb->score) - (sa->score < sb->score);
 354 }
 355
 356 int
 357 push_score (struct score_entry **scores, int *count, int newscore, char *username, char *newdata)
 358 {
 359  struct score_entry *newscores
 360    = (struct score_entry *) realloc (*scores,
 361                                      sizeof (struct score_entry) * ((*count) + 1));
 362   if (!newscores)
 363     return -1;
 364   newscores[*count].score = newscore;
 365   newscores[*count].username = username;
 366   newscores[*count].data = newdata;
 367   (*count) += 1;
 368   *scores = newscores;
 369   return 0;
 370 }
 371
 372 static void
 373 sort_scores (struct score_entry *scores, int count, int reverse)
 374 {
 375   qsort (scores, count, sizeof (struct score_entry),
 376         reverse ? score_compare_reverse : score_compare);
 377 }
 378
 379 static int
 380 write_scores (const char *filename, const struct score_entry *scores, int count)
 381 {
 382   FILE *f;
 383   int i;
 384   char *tempfile = malloc (strlen (filename) + strlen (".tempXXXXXX") + 1);
 385   if (!tempfile)
 386     return -1;
 387   strcpy (tempfile, filename);
 388   strcat (tempfile, ".tempXXXXXX");
 389 #ifdef HAVE_MKSTEMP
 390   if (mkstemp (tempfile) < 0
 391 #else
 392   if (mktemp (tempfile) != tempfile
 393 #endif
 394       || !(f = fopen (tempfile, "w")))
 395     return -1;
 396   for (i = 0; i < count; i++)
 397     if (fprintf (f, "%ld %s %s\n", scores[i].score, scores[i].username,
 398                 scores[i].data) < 0)
 399       return -1;
 400   fclose (f);
 401   if (rename (tempfile, filename) < 0)
 402     return -1;
 403   if (chmod (filename, 0644) < 0)
 404     return -1;
 405   return 0;
 406 }
 407
 408 static int
 409 lock_file (const char *filename, void **state)
 410 {
 411   int fd;
 412   struct stat buf;
 413   int attempts = 0;
 414   const char *lockext = ".lockfile";
 415   char *lockpath = malloc (strlen (filename) + strlen (lockext) + 60);
 416   if (!lockpath)
 417     return -1;
 418   strcpy (lockpath, filename);
 419   strcat (lockpath, lockext);
 420   *state = lockpath;
 421  trylock:
 422   attempts++;
 423   /* If the lock is over an hour old, delete it. */
 424   if (stat (lockpath, &buf) == 0
 425       && (difftime (buf.st_ctime, time (NULL) > 60*60)))
 426     unlink (lockpath);
 427   fd = open (lockpath, O_CREAT | O_EXCL, 0600);
 428   if (fd < 0)
 429     {
 430       if (errno == EEXIST)
 431         {
 432           /* Break the lock; we won't corrupt the file, but we might
 433              lose some scores. */
 434           if (attempts > MAX_ATTEMPTS)
 435             {
 436               unlink (lockpath);
 437               attempts = 0;
 438             }
 439           sleep ((rand () % 2)+1);
 440           goto trylock;
 441         }
 442       else
 443         return -1;
 444     }
 445   close (fd);
 446   return 0;
 447 }
 448
 449 static int
 450 unlock_file (const char *filename, void *state)
 451 {
 452   char *lockpath = (char *) state;
 453   int ret = unlink (lockpath);
 454   int saved_errno = errno;
 455   free (lockpath);
 456   errno = saved_errno;
 457   return ret;
 458 }
 459
 460
 461 /* update-game-score.c ends here */